Obviously they knew it was complex, but a lot of the issues, you have to have a game setting to discover. I can accept the argument that not having a beta was stupid, but simply delaying it wouldn't have solved a lot of the map glitches and connectivity issues, because they probably wouldn't have seen that stuff without actually having the game going, which meant having a beta, not delaying the launch (they could have had a beta 6 months ago and not changed the release date).
Of course they wanted it out for the holidays, and we also know that the media (more so, Sony fanboys) would have railed n Microsoft for a delay. With the way games have generally launched with issues (Unity, Advanced Warfare), having a week of complaints from users is FAR more tolerable than a month or two of complaints because of a launch delay that wouldn't fix things without a beta, most likely. Point being, they needed a beta, but I guess they cared more about nostalgia launching and such than getting complained at during a beta, in order to get the multiplayer right.
Lastly, the box doesn't mention it. All it says, vaguely, is, "[a]dditional storage, hardware, and Xbox Live may be required for setup, some updates, and features, including retention of some gameplay settings and information." That statement covers their patch, but not explicitly, and all the power to anyone who didn't stumble upon an article on the Internet and was mad over the issue. They definitely should have gone with 2 discs over a massive patch, as they're forcing DSL users to suffer hours (some probably over a day) to get that installed.